Technical Field
The present invention generally relates to a touch sensing circuit, and in particular, to the touch sensing circuit which is able to perform the fingerprint sensing.
Description of Related Art
In the capacitive fingerprint sensing technology nowadays, the capacitance characteristics of the finger ridge and the finger valley in the user's fingerprint are used to output different detecting signals, and by determining the detecting signals to achieve the fingerprint sensing. Therefore, additional scanning lines are needed to be arranged in the fingerprint sensing circuit to provide driving signals.
However, since high resolution are required by the fingerprint sensing to capture the relatively accurate fingerprint characteristics, the area of the sensing pads are limited, and the capacitance sensed is degraded accordingly, which results in the difficulties in processing and determining the detecting signals. In the present structure, the area of the sensing pads are further limited due to the arrangement of the additional scanning lines, or additional manufacturing process are needed to implement the sensing pads and the scanning lines in different metal layers, which increases the cost.
Therefore, the present fingerprint technology cannot provide sufficient driving signal while keeping the area of the sensing pads at the same time. As the area of the sensing pads in the circuit decreases, the sensed capacitance value of the fingerprint sensing decreases with the increasing thickness of the protection film and the difficulties of the fingerprint sensing rise accordingly.